sister-in-law
Americannoun
plural
sisters-in-law-
the sister of one's spouse.
-
the wife of one's brother or sister.
-
the wife of one's spouse's sister or brother.
noun
-
the sister of one's husband or wife
-
the wife of one's brother
Etymology
Origin of sister-in-law
First recorded in 1400–50; late Middle English syster in lawe; sister, in, law 1; from Middle English in-lawe “in law,” i.e., “a person within the regulation and protection of the law,” based on the prohibition by Roman civil law and, later, Christian canon law, of marriages within four degrees of consanguinity, i.e., up to and including first cousins
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The employee was his sister-in-law, the person confirmed.
From Los Angeles Times • Feb. 18, 2026
"Congratulations and you look amazing," Hague's sister-in-law Paris commented.
From BBC • Feb. 5, 2026
My sister-in-law, Eva Rose, who also lives nearby and also came to the intersection separately, described to me the moment the agents’ anger was unleashed a second time as she arrived 15 minutes later.
From Slate • Jan. 25, 2026
Charlie Pasarell, a tennis player who was one of ProServ’s early clients, introduced his sister-in-law, Marcee Fareed, to Craighill in 1978.
From The Wall Street Journal • Jan. 21, 2026
Emma bravely wrote to her sister-in-law Fanny, “Our sorrow is nothing to what it would have been if she had lived longer and suffered more.”
From "Charles and Emma: The Darwins' Leap of Faith" by Deborah Heiligman
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
